Michael Pachter, games industry analyst extraordinaire, has weighed in with his thoughts on the pricing of PS4 and Xbox One in an interview with Gamezone. He thinks Sony will settle on $349, while Microsoft will have a slightly higher starting price at $399. Sounds pretty reasonable to us. Of course, you never can tell what the exchange rate will be like as the consoles make it over to Europe. Pachter also said he believes both consoles would sell out at launch with these prices.
It should be noted that Pachter is only making an educated guess as to the prices. But in a couple of weeks we'll likely know exactly what we'll be paying for next-gen.